Cephalopod Mis-Education

Level_Head

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#1
The Internet has wondrous amounts of information; some of it is even true. But this page, for example, gets it badly wrong:

It's eHow's answer to the question "How does an octopus breathe?"--and here's the first paragraph:

The Mouth of an Octopus
The beak-like mouth of an octopus is located on the mantel cavity at the back of the bulbous head of the octopus, surrounded by the eight legs. The mouth is the entryway to the mantle cavity which has gills inside of it. The octopus uses these gills to breathe. Water is brought into the octopus mouth and is then passed through the gills back into the body of water. As the water is pushed over the surface of the gills, oxygen is picked up by the blood in the capillaries of the gills.
There are six significant problems here, by my count, not counting the misspelling of "mantel."
 

DWhatley

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#2
Oh dear, I expected that the answer was provided by a young person, both because of the errors and because of the way it was written:

About Me: Christy Flora has been writing professionally for more than fifteen years after winning her first awards for writing in the early 1980's. With a degree in Education, specializing in Organizational Leadership, Flora is an experienced, and published, author and editor. As a writer Flora has worked as an instructional designer spanning the genres of informational, educational and technical.
It might be best to highlight what is correct

The beak-like mouth of an octopus
The octopus uses these gills to breathe

I suspect the capillary transfer may be correct as well but that would be guessing, as she has done for the whole answer. Why would someone just make up this stuff?

I suspect that is not the best site for octo biology. Is there any cephalopod with more than one ink sac?
 

Level_Head

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#3
dwhatley;160552 said:
I suspect the capillary transfer may be correct as well but that would be guessing, as she has done for the whole answer. Why would someone just make up this stuff?
It's described that way in the literature, including in the paper on heartbeat that I posted in the "Three Hearts" thread.

She is apparently using a mixture of things she's read, misread, and perhaps guessed based on the "logic" of what makes sense for a land mammal. (Even with whales, the mammalian assumption of the mouth's connection to respiration doesn't work.)

dwhatley;160552 said:
I suspect that is not the best site for octo biology. Is there any cephalopod with more than one ink sac?
From my reading, no--this appears to be consistently a single rather than paired organ. That makes sense, as it seems to have evolutionarily been an extension off of the digestive tract, specifically the hindgut.

I don't know if the species without it show any signs--in other words, whether there is a vestigial trace of the ink sac. Ink sacs appear, rather famously, in belemnite fossils. Perhaps that artwork needs its own post.
 

DWhatley

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#4
That is what I thought (single ink sac) but on the same site there is an "answer" to a how do octopuses ink question and the answer person continually makes it plural.

I think Tony is setting up a forum for fact vs myth, keep tuned. I will move this thread to it when it gets established. Thanks for the initial, "Where would I put this? " question that was the instigator of what will likely be an interesting forum. To keep it self monitored, posters will be asked to point out the "myths" or misguidance with the references to keep valid oddities from becoming myths.
 

tonmo

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#8
I think Tony is setting up a forum for fact vs myth, keep tuned. I will move this thread to it when it gets established.
You're sitting in it now! :smile:
 

DWhatley

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#9
:oops: I was going to check to see if you had added it after I went through the posts, should have been first on my list since I now have an official moderating responsibility :razz:
 

GPO87

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#10
I like this new forum idea. There is so much confusion regarding cephs... I have trouble getting my friends to seperate fact from fiction! Thanks Tony!
Also... I will admit to mis-spelling "mantel". Oooo, maybe "mantle" is the Canadian way of spelling?:biggrin2: (looks around for support) eh? EH? *crickets chirping in background* yeah... i just need to use spell check more often.
 

Level_Head

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#11
GPO87;160646 said:
I like this new forum idea. There is so much confusion regarding cephs... I have trouble getting my friends to separate fact from fiction! Thanks Tony!
Also... I will admit to mis-spelling "mantel". Oooo, maybe "mantle" is the Canadian way of spelling?:biggrin2: (looks around for support) eh? EH? *crickets chirping in background* yeah... i just need to use spell check more often.
Maybe we could put something up on a mantelpiece. The two words once shared the same meaning, and it can be frustrating that both are correctly spelled. Around the 1500s, the two began diverging, with "mantel" referring to a temporary protective structure like a rigid tent used in battle, and eventually becoming the rigid structure over a fireplace. Here's one source.

The mantle (or pallium) is a protective bit of clothing, and both "mantle" and "pallium" are used for the cephalopod's cloak-like structure. Pallium is also used for the cloak-like structure of nerves surrounding the vertebrate forebrain, and even fish have this; it seems to be associated with spacial memory in lower vertebrates, which connected to a reference to spatial memory in octopuses here.

Pallium is still apparently a good word for the cephalopod. I rarely see it used, though, even in research papers, though the adjective "pallial" is generally used to refer to the nerve associated with the cephalopod mantle. Google[octopus pallium] and you'll get all sorts of hits for [octopus pallial] instead.

Back to the topic:

Probably the most common factual error on cephalopods is to assume that what is true for one is true for all of them, such as "octopuses have ink sacs" or "octopuses lay hundreds of thousands of eggs."
 

DWhatley

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#12
Probably the most common factual error on cephalopods is to assume that what is true for one is true for all of them, such as "octopuses have ink sacs" or "octopuses lay hundreds of thousands of eggs."
Excellent point! I don't know how many times I have muttered, but that is only for the ... species when reading or hearing something on a documentary. I don't get bent if the statement is generally true as trying to show exceptions would double the length of anything but when something is true about half or fewer (or only one or two of the species) I cringe.
 

forbidden_moose

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#13
i find with cephs that there is almost always an exception to any given rule, this always entertains me. Äll Octopuses live on the sea floor"is also a good one.
 

Level_Head

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#14
forbidden_moose;177731 said:
i find with cephs that there is almost always an exception to any given rule, this always entertains me. Äll Octopuses live on the sea floor"is also a good one.
That's one of those blanket [octopus] statements.
 

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